Very unhappy Customer

My car went in for repairs to replace rear bumper and light on 02/03/2016. I was told that the car should be ready on 24/03/2015. Even today its still not ready and I get excuses. The reason I'm told now why its not ready was because there was a delay in getting a bumper. Last week 01 APRIL 2016 I was promised that the car would be ready today, when they phoned me today 04 April they said there is a problem with the bumper it does not fit properly. How is that possible? They say they have ordered a new one and the other one was a second hand bumper. How is that possible as the assessor said the car should be fitted with a new bumper for over a month now? Please assist.